WHY ARE THESE PEOPLE SMILING? Mayor Bloomberg stands with Sanitation honchos on Sunday, hours before snow started piling up.Daniel Shapiro

Mayor Bloomberg yesterday had his “Katrina” moment — hailing his Sanitation commissioner amid a torrent of criticism over the department’s bungling of the blizzard cleanup.

Bloomberg warmly praised Sanitation Department boss John Doherty — and promised him his job was safe — in a moment reminiscent of then-President George W. Bush’s infamous endorsement of FEMA chief Michael Brown in the horrific aftermath of Hurricane Katrina, when Bush said, “Brownie, you’re doing a heck of a job.”

Doherty, who appeared on Bloomberg’s WOR-AM radio show, noted that he had been Sanitation commissioner for five years under Mayor Rudy Giuliani, followed by nine so far under Bloomberg.

“And I hope to do another three,” Doherty said, referring to the number of years left on Bloomberg’s current term.

Bloomberg quickly interjected: “You will do another three. That you don’t have to worry about.”

The mayor’s unflinching support for Doherty came after massive outcry over the city’s response to Sunday’s blizzard — which left many streets unplowed for days and wreaked havoc on emergency crews.

There have been allegations that some sanit workers engaged in a slowdown and even ignored some streets at the direction of their bosses, who are angry over upcoming budget cuts.

Doherty himself had only praise for the performance of his department’s workers.

“They did a great job. I’m very proud of them,” Doherty said on the mayor’s radio show.

Doherty even sent a memo to workers saying, “I want to thank each and every one of you for your dedication and endless hours of work during the recent blizzard.”

Bloomberg yesterday conceded that the snowstorm — and his administration’s handling of it — could affect his legacy and reputation as a manager.

The City Council is set to hold hearings on Jan. 10 on the blizzard response.

“OK, so now we’re going to take a reputational hit,” Bloomberg said. “Nobody’s perfect.”

State Sen. Malcolm Smith (D-Queens) called for “a formal investigation” of the allegations of a slowdown, saying he had also “heard it from sanitation workers that there was a concerted effort and were told not to move their trucks, to take their time” plowing city streets.

“We want e-mail trails, we want text-messaging, everything that was done prior to the snowstorm to find out exactly what happened,” Smith said.

A Department of Investigation spokesman said, “The DOI will look for any provable incidents of intentional acts.”